Cellulose Could Replace Short Glass Fibers in Composites

Wood and pulp giant Weyerhaeuser says it has figured out how to make a thermoplastic composite using engineered cellulose fiber from trees, instead of the short glass fibers usually used for reinforcement. Applications for the material include automotive parts and industrial components.

The composite, called THRIVE, is targeted at low-load applications such as office furniture, consumer appliances, kitchenware, and household goods, in addition to car parts. According to the company, compared to composites made with short glass fibers, or natural fibers like sisal, hemp, and kenaf, the new material has several advantages.

A new thermoplastic composite uses engineered cellulose fiber from trees, such as these logs in Kuopio, Finland, instead of the short glass fibers usually used for reinforcement. Applications include automotive parts and industrial components. (Source: Wikimedia Commons/Okko Pyykkö)

Injection-molding cycle times are up to 40 percent shorter than composites made with glass fibers, since the new material requires shorter pack-and-hold and cooling times. Mass is also reduced, since cellulose fiber is 40 percent less dense. Finished parts are up to 8 percent lighter. Short glass fibers are highly abrasive and hard on processing equipment, so cellulose fiber composites can reduce wear and tear. The composite's mechanical properties are similar, including tensile strength and flexural strength.

Several different composites have been made with natural fibers, including coconut fibers instead of traditional ceramic fibers in biocomposite tiles. The natural fibers improve the composite's strength and stiffness, and reduce their weight. Compared to an engineered material such as THRIVE, composites made with natural fibers can vary in quality from one batch to another. They also don't readily absorb dyes. In contrast, the new material easily absorbs dyes and demonstrates consistent performance characteristics between batches.

In addition, THRIVE composites are produced using a proprietary process that allows control of the dispersion of cellulose fibers within the polymer matrix. This allows for a smooth surface finish, which opens up new opportunities for the use of natural fibers in composite plastics. Conversely, if manufacturers prefer the fibers to be visible, they have that option as well."

The cellulose fiber is sourced partly from some of Weyerhaeuser's 20 million acres of forestland, which the company manages to third-party sustainability standards. Weyerhaeuser expects to produce the composite using its pulp manufacturing facilities. The material is provided as cellulose blended with polypropylene, with both high and low melt flow indices. It is available in both ready-to-mold thermoplastic pellets for molders, and in a masterbatch form for custom compounders.

The ratio of cellulose fiber to polymer in the composite can be changed to modify product strength and flexibility. From 10 percent to 40 percent, THRIVE cellulose fibers can be pre-blended with 60 percent to 90 percent of either virgin or pre-consumer recycled polypropylene. (Pre-consumer recycled is after manufacture but without consumer use, such as manufacturing waste byproducts.) The fibers can also be blended with ABS, PVC, low-density polyethylene (LDPE), high-density polyethylene (HDPE), or PLA and other biopolymers. Weyerhaeuser says it plans to expand the THRIVE line of products beyond polypropylene to include hydrocarbon and nonhydrocarbon polymers.

Ann, this looks like a great use of material. Glass fibers do tend to eat machinery and molds in normal application, so a less abrasive fiber would be great. Has there been any look at using these fibers in nylon applications? Also, is the cost of the additive similar to that of the glass fibers?

tekochip, that's a good point about flammability. The fact that Ford is working with Weyerhaeuser to develop materials for car interiors, plus the fact that these are engineered, not just natural, fibers, makes me think that potential problem may have already been addressed/compensated for. Here's a link to the MSDS for THRIVE, which gives a rating of 1 (0-4 scale): www.weyerhaeuser.com/pdfs/msds/501.pdf

Ann, ne thing I like about this product is that it is produced by materials we have naturally here in the US. With materials such as coconut, grow in a fairly narrow band of the planet. This tends to cause overharvesting in areas with low environmental controls.

Lou, I understand your POV on US materials sources. Actually Weyerhaeuser owns forests in various parts of the world and expects to source cellulose from them as needed. Forests that can be harvested for wood products in northern temperate zones (there aren't many in southern ones) are no longer as common as you might think, including in the US.

Hmm, 40% shorter mold times, comparable weight and material properties, less tooling damage during manufacturing, and blendability with a variety of plastic base material. What's not to like about the new THRIVE?

I agree with the flammability issue and the possible overharvesting of dwindling resources. Still, it seems to be a good idea.

Sounds like a waste product they are trying to find a use for. From the specs it's rreally just a filler pounded into dust so fine it won't show on the surface.

It's flamability is higher because it's so fine but the resin is more flamable so the point is moot. Wood actually is far less flamable than synthetic ones. The navy went to all polyster uniforms until they went up in flames regretfully with sailors in them so they switched back to cotton blends I believe.

That's an interesting story about polyester vs cotton and the flammability of natural vs synthetic materials. I remember as a kid in the 50s-60s hearing about the flammability of synthetic clothing material, which, I believe, is when many of the standards were developed for clothing material flammability.

Just as bad is it melting on the skin then when you slap it to put it out it sticks to the hand and spreads sticking to the skin where it was buring/melting. Not a good way to go.

Living in Fla pure polyster is just too hot and uncomfortable in the summer. Though I really like rayon which is about the most comfortable cloth usually, slightly better than cotton and doesn't seem as flamable as polyester or nylon. A good 65% cotton, 35% polyster works fairly well and cuts the problems of pure cotton or pure poly.

Jerry, that poly-cotton mix sounds like what I liked best for hiking clothes in my backpacking days. Cotton was supposed to be a no-no among backpacking enthusiasts because it takes so long to dry, either when wearing it, or when washing it at the campsite. But I found 100% polyester and other non-natural clothing to be too hot and sticky for comfort, no matter how it was made.

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